Thin-film magnetic head wafer and manufacturing method of thin-film magnetic head

ABSTRACT

A thin-film magnetic head wafer with a surface to be exposed by means of an optical stepper includes a plurality of thin-film magnetic head elements formed on the surface, and distance check regions that are flat in level and horizontal to the surface of the wafer, at least one of the distance check regions being formed on the surface within one exposure area of the optical stepper.

FIELD OF THE INVENTION

[0001] The present invention relates to a thin-film magnetic head waferon which a plurality of thin-film magnetic head elements formagnetically recording into and/or reproducing from a magnetic mediumsuch as a hard disk or a floppy disc are formed. The present inventionalso relates to a manufacturing method of a thin-film magnetic head.

DESCRIPTION OF THE RELATED ART

[0002] In general, when fabricating thin-film magnetic heads, variouswafer processes for forming many thin-film head elements on a wafer inmatrix are executed. Such wafer processes contain without exception aplurality of light exposure steps that typically use an optical stepper.

[0003] When performing a light exposure step using an optical stepper,it is necessary to confirm before each exposing operation that aposition of focus of an optical system in this stepper is correctlylocated on an image surface or image plane of the wafer and that theimage plane of the wafer is horizontal to the stepper. In order toperform these focus check and leveling check, detection of distancebetween the stepper and the image plane of the wafer will be required.

[0004] Since each magnetic head element formed on the thin-film magnetichead wafer is very tall, there are higher differences on the surface ofthe magnetic head wafer than on the surface of a semiconductor wafer. Inmost cases, these high differences are located even in regions used forfocus check and leveling check. Therefore, the focus and the levelingwill be checked based upon an average level or height of severalmagnetic head elements. The level of the head elements formed on notonly one wafer but also wafers fabricated in different lots may vary.Thus, accuracy of the focus check and the leveling check may lower, andsize and shape of resist patterns formed by using the stepper may becomeunstable causing yields to reduce.

[0005] It should be noted that no consideration has been taken beforefor accurately executing focus check and leveling check when performinga light exposure with respect to a thin-film magnetic head wafer.

SUMMARY OF THE INVENTION

[0006] It is therefore an object of the present invention to provide athin-film magnetic head wafer and a manufacturing method of a thin-filmmagnetic head, whereby continued accuracy in focus check and levelingcheck in case of an exposure process can be assured.

[0007] According to the present invention, a thin-film magnetic headwafer with a surface to be exposed by means of an optical stepperincludes a plurality of thin-film magnetic head elements formed on thesurface, and distance check regions that are flat in level andhorizontal to the surface of the wafer, at least one of the distancecheck regions being formed on the surface within one exposure area ofthe optical stepper.

[0008] At least one of distance check regions is formed on the surfaceof the wafer within one exposure area of the optical stepper, and thedistance check region is kept flat and horizontal to the surface of thewafer. Thus, high accuracy of the focus check and the leveling check canbe maintained. As a result, size and shape of resist patterns formed byusing the stepper can be kept stable resulting yields to increase.

[0009] It is preferred that the distance check regions include a regionfor checking focus of the optical stepper with respect to the wafer.

[0010] It is also preferred that the region for checking focus is formedonly one within one exposure area of the optical stepper and/or that theregion for checking focus is formed at center portion of the oneexposure area of the optical stepper.

[0011] It is preferred furthermore that the distance check regionsinclude regions for checking leveling of the wafer with respect to theoptical stepper.

[0012] It is also preferred that the plurality of regions for checkingleveling are formed within one exposure area of the optical stepper,and/or that the regions for checking leveling are formed at borderingportions in the one exposure area of the optical stepper.

[0013] Preferably, the regions for checking leveling are formed to besplit across a boundary between the exposure area and an adjacentexposure area of the optical stepper.

[0014] It is preferred that the distance check regions have surfaceswith a level equal to that of a reference surface of the wafer, or thatthe distance check regions have surfaces with a level equal to that of athin-film layer or thin-film layers deposited on the reference surfaceof the wafer.

[0015] According to the present invention, furthermore, a manufacturingmethod of thin-film magnetic heads on a wafer with a surface to beexposed by means of an optical stepper, includes a step of formingdistance check regions that are flat in level and horizontal to thesurface of the wafer, at least one of the distance check regions beingformed on the surface within one exposure area of the optical stepper,and a step of checking a distance between the optical stepper and thesurface to be exposed by using at least one of the formed distance checkregions.

[0016] It is preferred that the checking step includes a step ofchecking focus of the optical stepper with respect to the surface of thewafer by using one of the formed distance check regions, and/or that thechecking step includes a step of checking leveling of the surface of thewafer with respect to the optical stepper by using of the formeddistance check regions.

[0017] It is also preferred that the forming step includes a step ofinhibiting formation of thin-film layer on the distance check regions sothat the distance check regions have surfaces with a level equal to thatof a reference surface of the wafer, or that the forming step includes astep of depositing a flat thin-film layer or flat thin-film layers onthe distance check regions so that the distance check regions havesurfaces with a level equal to that of a thin-film layer or thin-filmlayers deposited on the reference surface of the wafer.

[0018] Further objects and advantages of the present invention will beapparent from the following description of the preferred embodiments ofthe invention as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 shows a plane view schematically illustrating a thin-filmmagnetic head wafer, exposure area each of which corresponds to oneexposure of an optical stepper, focus check regions and leveling checkregions of a preferred embodiment according to the present invention;

[0020]FIG. 2 shows a plane view illustrating in detail the area in oneexposure, the focus check region and the leveling check regionsaccording to the embodiment shown in FIG. 1;

[0021]FIG. 3 illustrates a relationship between a position of focus andan obtained resist width in a resist exposure step when forming acritical layer;

[0022]FIG. 4 illustrates configuration of an example of an opticalsystem for the focus check and the leveling check;

[0023]FIG. 5 shows a plane view illustrating another configuration ofthe leveling check region according to the present invention; and

[0024]FIG. 6 shows a plane view illustrating a further configuration ofthe leveling check region according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] In FIG. 1, reference numeral 10 denotes a thin-film magnetic headwafer for forming many thin-film head elements thereon in matrix. Ineach of exposure steps that are performed several times during eachthin-film fabrication process of the wafer, an optical steppersequentially exposes a plurality of exposure areas 11. In each exposurearea 11 used for one exposing operation of the stepper, a pattern ofmany thin-film magnetic head elements 12 is exposed as shown in FIG. 2.

[0026] In each exposure area 11 on the wafer 10, furthermore, a regionused for checking focus position (in this specification this region iscalled as focus check region) 13 and regions for checking leveling (inthis specification these regions are called as leveling check regions)14 are prepared. Preferably, a single focus check region 13 may beprepared at center portion of the exposure area 11 as shown in FIG. 2.Four leveling check regions 14 may be prepared at four corners of theexposure area 11, respectively. The number and position of these focuscheck region 13 and leveling check regions 14 are not limited to this.For example, two leveling check regions 14 may be prepared at diagonallyopposite positions in the exposure area 11.

[0027] In the focus check region 13 and also in the leveling checkregions 14, no element is formed. The surfaces within the focus checkregion 13 and the leveling check regions 14 are kept flat and horizontalto the surface of the wafer 10. Namely, when fabricating the thin-filmlayers on the wafer 10, no layer is deposited within the focus checkregion 13 and the leveling check regions 14 so that their surfaces havea plane level equal to a reference surface of the wafer 10. Alternately,each of multi-layers to be sequentially deposited in accordance with thefabricating processes of the thin-film magnetic head elements isdeposited in flat on the wafer reference surface in the focus checkregion 13 and the leveling check regions 14 so as to represent level ofthe layers at each fabricating process. According to the latter case,since the level at the focus check region 13 and the leveling checkregions 14 represents the level of the laminated layers at that time,deviations of the focus due to variations in the thickness of thedeposited layers within a wafer or between lots of wafers can beautomatically compensated. The leveling check regions 14 within eachexposure area 11 should be formed to have the same level with eachother.

[0028] The focus check region 13 and the leveling check regions 14 maybe formed in a rectangular shape with a size of 0.3-2.0 mm×0.3-2.0 mm, acircular shape with a diameter of 0.3-2.0 mm or an ellipse shape with adiameter of 0.3-2.0 mm×0.3-2.0 mm. However, their shape is not limitedto these shapes. The size of the regions 13 and 14 is also not limitedto the above-mentioned sizes but will be determined so that the majorportion, for example 80%, of beam used for focus check and for levelingcheck is applied within each region.

[0029] There are several processes for forming “critical layers” in thefabricating process of the thin-film magnetic heads. The “criticallayers” means layers with very narrow patterns that must form with highaccuracy. FIG. 3 is a graph illustrating a relationship between aposition of focus and an obtained resist width in a resist exposurestep. This relationship is based upon a resist material used in one ofthe processes for forming the critical layers and upon conditions forprinting the resist material. In the graph, a focus position of 0 (μm)indicates that the focus of the stepper is correct.

[0030] In general, such critical layer forming process is required tokeep the printing precision of the resist material within a range ofabout ±10%. Therefore, in case that a target resist width is 0.3 μm, theresist pattern must be formed with a resist width within a range of0.3±0.03 μm.

[0031] As shown in the graph of FIG. 3, no resist pattern can be formedwhen the focus position is less than −0.4 μm, and there is tendency toincrease the obtained resist width when the focus position is 0.6 μm ormore. Therefore, it is necessary to contain the focus accuracy within arange of ±0.4 μm in order to obtain the above-mentioned precision of theresist width. To obtain more improved resist width precision, it isdesired that the focus accuracy is controlled within a range of ±0.2 μm.

[0032] It is apparent that the similar focus accuracy as shown in FIG. 3will be required in the remaining processes for forming the criticallayers.

[0033] If there is a difference in level on the surface in the focuscheck region 13 exerted on the checking of the focus and if portionother than the difference portion has a reference level with a level orheight of zero, the detected focus position will depend on the productof a level or height of the difference portion and a ratio of an area ofthe difference portion with respect to an area of the whole region.Suppose that the ratio of the difference portion area with respect tothe whole region area is 50%. In this case, to obtain the aforementionedresist width accuracy, the height of the difference in level should belimited to 0.8 μm or less, preferably to 0.4 μm or less.

[0034] Typically, the beam spot used for the focus check has a size ofabout 0.2 mm×1.0 mm. If the surface of such beam spot area used for thefocus check is uniformly inclined to the stepper, it is possible tocheck whether the focus is correct or not based upon an average value ofthe distances between the inclined surface and the stepper. However, ifthe surface inclines too much, the reflected beam never return to alight sensor and thus no check of the focus is possible anymore.Therefore, the inclination of the surface of the focus check region 13that is the region for measuring distance to check the focus ispreferably limited to 5 or less with respect to the wafer surface.

[0035] The aforementioned ranges of difference in level and inclinationof the surface of the focus check region 13 are similarly adapted to theranges of difference in level and inclination of the surface of theleveling check regions 14.

[0036]FIG. 4 illustrates configuration of an example of an opticalsystem for checking the focus and the leveling using such focus checkregion 13 and leveling check regions 14.

[0037] In the figure, reference numeral 40 denotes an optical fiber fortransmitting light from a light source such as a mercury lamp (notshown), 41 a light transmitting slit, 42 a fixed mirror, 43 a projectionlens, 44 a slit image projected on the wafer 10, 45 a condenser lens, 46a rotational oscillation mirror, 47 a light receiving slit and 48 alight sensor.

[0038] In order to check the focus, the slit image 44 is projected andformed onto the focus check region 13 in the exposure area 11 on thewafer 10, and then it is checked whether a reflected slit light from thefocus check region 13 through the light receiving slit 47 can bedetected by the light sensor 48 or not. If the surface of the wafer 10locates at the correct focus position, the reflected slit light can bedetected. Otherwise, no slit light can be detected.

[0039] The similar operations are executed at each leveling checkregions 14 in the exposure area 11 to check the leveling.

[0040] According to the aforementioned embodiment, the single focuscheck region 13 which is kept flat and horizontal to the surface of thewafer 10 is formed in each exposure area 11 that is used for oneexposing operation of the stepper, and four leveling check regions 14which are kept flat and horizontal to the surface of the wafer 10 isformed in the same exposure area 11. Thus, high accuracy of the focuscheck and the leveling check can be maintained, and size and shape ofresist patterns formed by using the stepper can be kept stable resultingyields to increase.

[0041]FIG. 5 illustrates another configuration of the leveling checkregion according to the present invention.

[0042] In the figure, reference numeral 51 denotes an exposure area usedfor one exposing operation of the stepper, 53 a single focus checkregion prepared at center portion of the exposure area 51, and 54 fourleveling check regions prepared at four edges of the exposure area 51.Each leveling check region 54 is split in two across a boundary betweenthe two adjacent exposure areas 51. The splitting ratio may be even oruneven with each other.

[0043] Since each leveling check region 54 is arranged to be splitacross a boundary between the two adjacent exposure areas 51, an areaoccupied by the leveling check regions 54 in one exposure area 51reduces and thus effective use of the wafer can be attained.

[0044]FIG. 6 illustrates a further configuration of the leveling checkregion according to the present invention.

[0045] In the figure, reference numeral 61 denotes an exposure area usedfor one exposing operation of the stepper, 63 a single focus checkregion prepared at center portion of the exposure area 61, and 64 fourleveling check regions prepared at four corners of the exposure area 61.Each leveling check region 64 is split in four across boundaries amongthe four adjacent exposure areas 61. The splitting ratio may be even oruneven with each other.

[0046] Since each leveling check region 64 is arranged to be splitacross boundaries among the four adjacent exposure areas 61, an areaoccupied by the leveling check regions 64 in one exposure area 61further reduces and thus more effective use of the wafer can beattained.

[0047] Many widely different embodiments of the present invention may beconstructed without departing from the spirit and scope of the presentinvention. It should be understood that the present invention is notlimited to the specific embodiments described in the specification,except as defined in the appended claims.

What is claimed is:
 1. A thin-film magnetic head wafer with a surface tobe exposed by means of an optical stepper, said wafer comprising: aplurality of thin-film magnetic head elements formed on said surface;and distance check regions that are flat in level and horizontal to saidsurface of said wafer, at least one of said distance check regions beingformed on said surface within one exposure area of said optical stepper.2. The wafer as claimed in claim 1, wherein said distance check regionscomprise a region for checking focus of said optical stepper withrespect to said wafer.
 3. The wafer as claimed in claim 2, wherein saidregion for checking focus is formed only one within one exposure area ofsaid optical stepper.
 4. The wafer as claimed in claim 2, wherein saidregion for checking focus is formed a t center portion of said oneexposure area of said optical stepper.
 5. The wafer as claimed in claim1, wherein said distance check regions comprise regions for checkingleveling of said wafer with respect to said optical stepper.
 6. Thewafer as claimed in claim 5, wherein said plurality of regions forchecking leveling are formed within one exposure area of said opticalstepper.
 7. The wafer as claimed in claim 5, wherein said regions forchecking leveling are formed at bordering portions in said one exposurearea of said optical stepper.
 8. The wafer as claimed in claim 5,wherein said regions for checking leveling are formed to be split acrossa boundary between said exposure area and an adjacent exposure area ofsaid optical stepper.
 9. The wafer as claimed in claim 1, wherein saidwafer has a reference surface, and wherein said distance check regionshave surfaces with a level equal to that of said reference surface ofsaid wafer.
 10. The wafer as claimed in claim 1, wherein said wafer hasa reference surface, and wherein said distance check regions havesurfaces with a level equal to that of a thin-film layer or thin-filmlayers deposited on said reference surface of said wafer.
 11. Amanufacturing method of thin-film magnetic heads on a wafer with asurface to be exposed by means of an optical stepper, said methodcomprising the steps of: forming distance check regions that are flat inlevel and horizontal to said surface of said wafer, at least one of saiddistance check regions being formed on said surface within one exposurearea of said optical stepper; and checking a distance between saidoptical stepper and said surface to be exposed by using at least one ofsaid formed distance check regions.
 12. The manufacturing method asclaimed in claim 11, wherein said checking step comprises a step ofchecking focus of said optical stepper with respect to said surface ofsaid wafer by using one of said formed distance check regions.
 13. Themanufacturing method as claimed in claim 11, wherein said checking stepcomprises a step of checking leveling of said surface of said wafer withrespect to said optical stepper by using of said formed distance checkregions.
 14. The manufacturing method as claimed in claim 11, whereinsaid wafer has a reference surface, and wherein said forming stepcomprises a step of inhibiting formation of thin-film layer on saiddistance check regions so that the distance check regions have surfaceswith a level equal to that of said reference surface of said wafer. 15.The manufacturing method as claimed in claim 11, wherein said wafer hasa reference surface, and wherein said forming step comprises a step ofdepositing a flat thin-film layer or flat thin-film layers on saiddistance check regions so that the distance check regions have surfaceswith a level equal to that of a thin-film layer or thin-film layersdeposited on said reference surface of said wafer.